<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    div{
      width: 100px;
      height: 100px;border: 1px solid red;
    }
    div:hover{
      /*margin: 20px 0 0 20px;*/
      /*相对定位:元素不脱离文档流*/
      position: relative;
      /*通过left/right/top/bottom相对于元素初始位置偏移*/
      bottom: -20px;
      right: -20px;
    }
  </style>
</head>
<body>
<div>div1</div>
<div>div2</div>
<div>div3</div>
</body>
</html>